Much of the electrical power distribution system is mounted on poles above the ground, and virtually all of the electrical transmission lines are mounted on poles or towers above the ground. Both distribution and transmission systems always include some form of automatically operable switch means for deenergizing the line in the event of an electrical fault. Such switch means are primarily for the purpose of protecting the electrical equipment in the event of a short circuit or an overload. Nevertheless, the automatic switch means will sometimes deenergize a power line because of a broken wire, damaged pole or tower structure or the like. The difficulty arises in the event wherein an electrical wire has broken and is lying close to the ground, or simply sagging due to lack of support or the like, and being disposed relatively close to the ground. In many situations, these events occur without sufficient contact between two or more wires to cause the automatic switch means to deenergize the power line. For example, if a tree limb falls and breaks a single wire on a pole, the wire may fall to the ground, but not engage the ground firmly enough to cause the flow of sufficient current to operate the automatic switch means. The result is that a live electrical power line is in a position to be engaged by people, which can be very hazardous. Also, a pole might be broken, and the entire top of the pole may stay intact so that a portion of the pole, along with the crossarms, will be supported from the wires, carried by the two adjacent poles. In such a situation, the wires may be close enough to the ground to be engaged by pedestrians or vehicles, but it is very likely that the electrical conductors will not touch one another firmly enough to operate the automatic switch means.
There has been some effort in the past to resolve these problems. U.S. Pat. No. 4,616,287 to Reedy discloses a transverse rod fixed to the neutral conductor on the pole line. The idea is that if a phase line breaks, the phase line will engage the transverse rod and cause a direct short circuit to the ground line, which will operate the automatic switch means. It will be obvious that such a system will not be effective in the event a pole is broken off as is discussed above.
Another prior art effort at solving the above mentioned problems is shown in U.S. Pat. No. 556,823 issued to Jewett. The Jewett device senses the position of a wire, and creates a short circuit in the event the wire is either missing or is extremely low. However, the Jewett device is open so that it would be hazardous to service people working on the lines, and is so constructed that a less-than-serious fault on the lines might cause a short circuit, to interrupt the electric power.
Thus, the prior art does not provide an adequate solution for the above stated problems.